The invention relates generally to a device for applying a treatment liquid, and more particularly to a device for applying a treatment liquid to a moving web of material such as a textile web.
Such a device is disclosed in German Provisional Patent 10 78 527. In the particular device disclosed therein, the follower limiting element consists of a second drum, which is arranged at the same level as the first drum. The first and second drums form a roll nip through which the fabric web passes from top to bottom. The nip formed by the drum is filled up to a certain level with treatment liquid that is supplied from a supply disposed thereabove. The sealing elements are formed from stationary disks that sealingly abut against the front ends of the two drums.
The above-mentioned device is not suitable for all situations. A certain line pressure must be exerted along the roll nip to make it impermeable. This line pressure limits the quantity of liquid that is applied and, moreover, may attack the fabric web in a way that is not tolerated by all types of fabric. The stationary sealing elements at the ends of the nip, which the drums slide past, are susceptible to wear and must be replaced often if the configuration is to remain impermeable.
U.S. Pat. No. 2,729,192 discloses a coating device, in which the fabric web runs horizontally up against a drum and then runs down its side. In the downwardly directed area, a type of wiper abuts the fabric web or the drum. This wiper, in turn, borders on a nip in which treatment liquid is found, which then passes over on to the fabric web. The disadvantage of this device is that the fabric web only contacts the treatment liquid on one side. In addition, it is necessary to run the fabric web along the edge of the wiper, causing friction. To retain the impermeable nature of the nip, the contact force of the edge of the wiper must not exceed a certain value. The resulting friction is not tolerated by all fabrics, such as woven and knitted fabrics.
German Patent 29 35 413 discloses a coating device for foam in which the fabric web runs horizontally at the bottom onto a drum. The web wraps around this drum for at least 180.degree., and is then led away from the drum, returning to the top. In the lower region, a nip is formed by a boundary surface which is directed diagonally to the drum and which is limited at the lower end by a narrow gap. This narrow gap can be formed by a pipe or the like, which leaves a clearance space from the periphery of the drum. Foam that had been introduced into the nip is removed through this gap. The foam then forms a thin layer on the drum surface and is carried along until the fabric web is placed from the outside against the foam layer on the drum surface in the lower region of the drum. This device also has the capability of applying the foam on only one side. However, the device is not suitable for treatment liquids, because a treatment liquid does not retain its shape and would simply flow out through the gap at the lower end of the nip.
The present invention is directed to providing a device for applying a treatment liquid which is reliable in operation and which can apply the liquid to a sensitive fabric web.